N64.4 vs R21
N64.4 (Mastodynia) compared with R21 (Rash and other nonspecific skin eruption), from the official CMS tabular data. Both may be reported when both conditions are documented (Excludes2).
Can these codes be reported together?
Yes, when both are documented. R21 carries an Excludes2 note covering N64.4: “symptoms relating to breast (N64.4-N64.5)”
Excludes2 marks distinct conditions — both may be reported when both are documented.
Side by side
| N64.4Mastodynia | R21Rash and other nonspecific skin eruption | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | N00-N99 — Diseases of the Genitourinary System (N00-N99) | R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99) |
| Definition | Mastodynia is a billable ICD-10-CM diagnosis code (N64.4). | Rash and other nonspecific skin eruption is a billable ICD-10-CM diagnosis code (R21). |
| Includes | — | rash NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources